Synthetic natural gas production

ABSTRACT

A process for the production of synthetic natural gas or town gas is described wherein the hot gaseous product of the partial combustion of a carbonaceous fuel, containing hydrogen and carbon monoxide, is passed into a carburetting zone at a temperature of from 700 to 1100*C and therein enriched with a volatile hydrocarbon carburant which on evaporation into the hot gaseous product of partial combustion is thermally cracked into methane and lighter unsaturated hydrocarbons. The carburetted gas product is then passed into a hydrogenation zone maintained at a temperature sufficient to further decompose any remaining hydrocarbon carburant and to hydrogenate the unsaturated hydrocarbons. In this process coke formation in the carburetting zone is substantially minimized by introducing the volatile hydrocarbon carburant into the carburetting zone in the form of a thin layer of liquid which is maintained at a temperature below that at which thermal cracking occurs during the time the carburant is not adsorbed by the hot gas stream.

United States Patent [191 Van den Berg et al.

[451 Nov. 4, 1975 SYNTHETIC NATURAL GAS PRODUCTION [75] Inventors:Godfried J. Van den Berg; Frank K. G. Ouwerschuur, The Hague, both ofNetherlands [73] Assignee: Shell Oil Company, Houston, Tex.

[22] Filed: Dec. 5, 1973 [21] Appl. No.: 422,051

[30] Foreign Application Priority Data Dec. 15, 1972 Netherlands 7217059[52] US. Cl 48/199 R; 48/116; 48/205; 48/219; 239/434.5; 261/157;261/DIG. 54

[51] Int. Cl. C10J H20 [58] Field of Search 48/219, 205, 215, 202,48/199 R, 199 FM, 197 FM, 197 R, 144, 116,118,109, 96,196 R; 261/118, 78A,

DIG. 54, 157; 259/4; 239/434, 434.5, 132.3

[56] References Cited UNITED STATES PATENTS 2,716,597 8/1955 Linder48/197 R 2,971,829 2/1961 Van Rossum 48/215 Primary ExaminerS. LeonBashore Assistant ExaminerGeorge C. Yeung [57] ABSTRACT A process forthe production of synthetic natural gas or town gas is described whereinthe hot gaseous product of the partial combustion of a carbonaceousfuel, containing hydrogen and carbon monoxide, is passed into acarburetting zone at a temperature of from 700 to ll00C and thereinenriched with a volatile hydrocarbon carburant which on evaporation intothe hot gaseous product of partial combustion is thermally cracked intomethane and lighter unsaturated hydrocarbons. The carburetted gasproduct is then passed into a hydrogenation zone maintained at atemperature sufficient to further decompose any remaining hydrocarboncarburant and to lhydrogenate the unsaturated hydrocarbons. In thisprocess coke formation in the carburetting zone is substantiallyminimized by introducing the volatile hydrocarbon carburant into thecarburetting zone .in the form. of a thin layer of liquid which ismaintained at a temperature below that at which thermalcracking occursduring the time the carburant is not adsorbed by the hot gas stream.

2 Claims, 3 Drawing Figures US. Patent Nov. 4, 1975 Sheet 10f2 3,917,468

FIG. 2

US. Patent Nov. 4, 1975 Sheet 2 of2 3,917,468

SYNTHETIC NATURAL GAS PRODUCTION BACKGROUND OF THE INVENTION Thisinvention relates to an improved process for production of a syntheticnatural gas of sufficient calorific value to be of use as town gas. Moreparticularly, this invention is directed to a process wherein thegaseous product of partial combustion, being composed mainly of hydrogenand carbon monoxide which have relatively low calorific value, isupgraded in fuel value by mixing (carburetting) said gaseous productwith the vapors of a volatile hydrocarbon at a temperature sufficient tothermally crack the hydrocarbon into methane and light unsaturatedhydrocarbons, which are subsequently hydrogenated to afford a high-fuelvalue town gas, while at the same time avoiding problems tocokeformation which are inherent in such a carburetting procedure.

In processes for the partial combustion of fuels such as, inter alia,heavy fuel oil, petroleum distillates or residues, liquid fuelcontaining process soot or slurries of coal grit in water, a gasprincipally containing hydrogen and carbon monoxide is obtained attemperatures above approximately lOC. In such processes some soot isinevitably formed and this gives rise to a suspension of fine sootparticles in the hot gas produced.-

The gas thus produced has a relatively low calorific value, this beingusually in the range of 1000 to 3000 kcal./Nm In order to be used astown gas, however, a calorific value of more than 5000 kcal./Nm isgenerally required. The required increase in calorific value can beeffected by combining the gas product of partial combustion, maintainedat a temperature between 700 and 1 100C, with a stream of lighter weightvolatile hydrocarbons which evaporate into the gas stream and aresubsequently pyrolyzed. This procedure which for clarity and conveniencewill be designated herein as carburetting the hot gas product of partialcombustion with a volatile hydrocarbon carburanti.e., the gas product ofpartial combustion is enriched by mixing with volatile carboncompounds-results in the formation of methane and lighter unsaturatedhydrocarbon compounds in the gas stream. This carburetted gas stream isthen suitably passed into a hydrogenation zone maintained at a hightemperature to further crack any remaining hydrocarbon carburant and tohydrogenate the unsaturated compounds thereby affording a high fuelvalue synthetic natural gas or town gas. If desired steam may beinjected into the gas before, during or after carburetting in order toreduce soot formation. For efficient carburetting the presence of anexcess amount of hydrogen is required. Gas obtained by partialcombustion usually meets this requirement; there is a sufficient amountof hydrogenation to either prevent or essentially repress the formationof additional soot.

In a typical down stream processing scheme the hot carburetted gasleaving the hydrogenator is cooled, for example to a temperature atwhich the soot and any hydrogen sulfide may be removed from it or atwhich a catalytic conversion of the carbon monoxide or a catalyticmethane treatment can be carried out, and then desirably is furthercooled in a waste heat boiler, since the amount of available heat isconsiderable and may be applied for the production of high pressuresteam. Since the gas usually contains soot, it is desirable to employ awaste heat boiler in which the hot gas is passed through helically-woundtubes which are externally 2 cooled by means of boiling water. The sootdeposits less readily on the walls of the helical tubes than it does onthe walls of straight tubes. The tubes therefore do not become chokedwith soot.

While the processing scheme, described above in general terms, wouldseem to be a rather attractive way of increasing the calorific value ofthe gas product of partial combustion, there is a problem relating tothe use of conventional procedures and apparatus in the carburettingstep which substantially detract from the viability of the overallprocess. In conventional carburetting techniques the liquid hydrocarboncarburant is injected directly into the hot carburetting zone (heatedvia contact with the hot gas stream from partial combustion) by means ofan injection nozzle at rather high velocity relative to the velocity ofthe hot gas stream. Typically, the hot gas velocity ranges from 1-3m/sec while the velocity for the carburant on injection into thecarburetting zone ranges from 10-40 m/sec. When these conventionalinjection techniques are employed it has been found that a small part ofthe liquid carburant flows over the rim of the injection nozzle and intoan area where little hydrogen and much carburant is present. This givesrise to pyrollytic cracking and to the accumulation of solid substances.It is not quite certain whether this is coked oil, i.e., carbon or tarryand gummy substances having a very high molecular weight and a highcarbon content. One of the possibilities is polymerization ofunsaturated compounds being formed. The accumulations are found in thecarburetting zone in the immediate vicinity of and on the injectionnozzle for the carburant. For most efficient operation theseaccumulations should be removed periodically and this requires the wholeprocess to be stopped. This is an expensive and difficult operationwhich, moreover, causes inconvenience for the consumer of the gasproduced. It is even possible that considerable reductions in thediameter of the carburetting zone will occur as a consequence of theaccumulation of the said solid substances. In this case the pressure inthe partial combustion of gasification reactor upstream of thecarburetting zone may rise to unacceptably high levels.

The present invention provides a solution for these and similarproblems.

SUMMARY OF THE INVENTION It has now been found that the carbon or cokeaccumulation which occurs in the carburetting zone of the processdescribed above, wherein the hot gas product of partial combustion iscarburetted with a volatile hydrocarbon, can be substantially avoided ifthe liquid hydrocarbon carburant is passed. into the carburetting zonein a thin layer on carburetting zone surfaces which are cooled byexternal means "to such an extent that during the time that thecarburant is not adsorbed by the hot gas it is maintained and remains ata temperature below which thermal cracking occurs. Accordingly, theinstant invention provides a process for the production of syntheticnatural gas or town gas which comprises a. partially combusting acarbonaceous fuel in a par tial combustion zone to produce a hot gaseousproduct containing hydrogen and carbon monoxide;

b. carburetting the hot gas product of the partial combustion zonemaintained at a temperature of between 700 and 1 C with a volatileliquid hydrocarbon carburant in a carburetting zone thereby effectingvolatilization of the carburant into the hot gas and the accompanyingthermal cracking of the carburant into methane and lighter unsaturatedhydrocarbons, said liquid carburant being introduced into thecarburetting zone in the form of a thin layer maintained at atemperature below that at which thermal cracking occurs during the timethe carburant is not absorbed by the hot c. passing the carburettedproduct of the carburetting zone into a hydrogenation zone maintained atelevated temperatures wherein any remaining volatilized hydrocarboncarburant is further decomposed by thermal cracking and the unsaturatedhydrocarbon compounds are hydrogenated and;

d. cooling the hot gaseous product of the hydrogenation zone.

In the operating according to the process of this invention, it has beensurprisingly found that carburetting is not adversly affected when theinjection of the carburant into the gas to be carburetted is not carriedout under high pressure or at a great speed and as directly as possibleas is dictated by conventional procedures. That is, with the instantprocess it is essential that the carburant be introduced into thecarburetting zone at a velocity which is considerably lower than whenthe carburant is injected by means of an injection nozzle char=acteristic of conventional processes. Thus, the process of the instantinvention not only avoids the accumulation of coke or carbon deposits inthe carburetting zone; but additionally does not require that thepressure of the carburant be raised in advance of injection to a valuewell above the pressure of the gas in the carburetting zone in order toachieve high carburant injection velocities.

In carrying out the carburetting step according to this invention it iscritical that the hydrocarbon carburant be introduced into thecarburetting zone in the form of a thin layer of liquid which ismaintained below the cracking temperature of the carburant before it isabsorbed by (volatilized into) the gas to be carburetted. Accordingly,another aspect of this invention is concerned with an apparatus forcarburetting the hot gas product of the partial combustion of acarbonaceous fuel with a volatile hydrocarbon carburant wherein theliquid carburant is supplied to the carburetting zone as a thin layer orfilm which is maintained below cracking temperatures by externallysupplied cooling on all those surfaces of the carburetting zone in whichthe carburant is in contact before it is absorbed in the gas to becarburated.

THE DRAWINGS The invention will be described in greater detail withreference to the accompanying drawings. These drawings which illustratethe process and apparatus of the present invention are intended to beillustrative rather than limiting on its scope.

FIG. 1 is a lateral view of an apparatus set up suitable for carryingout the process of the invention.

FIG. 2 is a partial cross-section of the carburetting apparatusaccording to the invention taken along line 2-2 of FIG. 1.

FIG. 3 is a diagrammatic drawing of an alternative embodiment of thecarburetting apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In basic terms the inventionrelates to a process and apparatus for the production of a syntheticnatural gas or town gas having a calorific value of more than 1,000kcal. per Nm by partially combusting a carbonaceous fuel in a partialcombustion zone comprising a refractory gasification reactor,carburetting the hot gas from the gasification reactor with a carburantat a temperature between 700C and 1 C in a carburetting zone whichconnects the gasification reactor to a hydrogenation zone, conductingthe desired reactions in the carburetted gas in the hydrogenation zone(reactor) and cooling the gas obtained from the hydrogenation zone.

The first step of the process according to the invention involves atypical partial combustion procedure wherein a conventional carbonaceousfuel source, such as those detailed above (heavy fuel oil, coal grit,etc), is combined with less than the theoretical amount of oxygenpresent in an oxygen-containing gas at temperatures in excess of 1000Cto yield a gaseous product containing as principal components, hydrogenand carbon monoxide. Since this step of the process is whollyconventional and quite well known by those skilled in the art it neednot be detailed further herein.

The hot gas product of the partial combustion zone is then passed intothe carburetting zone where it mixed with a volatile liquid hydrocarboncarburant, the mixing occuring substantially in the vapor state. Thetemperature of the hot gas throughout the carburetting zonerangessubstantially between 700 and 1l0OC. This temperature is sufficient tocause the hydrocarbon carburant to thermally crack into methane andlower unsaturated hydrocarbon compounds on vaporization into the hot gasstream. As indicated above, it is critical that the liquid carburant besupplied to the carburetting zone as a thin layer or film which ismaintained at a temperature below that at which it begins to undergothermal cracking during the time that the carburant is not absorbed bythe hot gas stream. To maintain the liquid carburant as a thin film onthe carburetting zone surface it is generally necessary to supply thecarburant at injection velocities below those encountered withconventional injection nozzle systems. The rate at which the carburantis introduced unto the carburetting zone for purposes of this inventioncan be conveniently expressed in terms of residence time in the carburetting zone, thus eliminating any dependence on specific carburettingzone size and shape. Although for the process of the invention it is inprinciple permissible to have residence times of up to 10 seconds forthe usual types of carburant, the residence time of the liquid carburantin the carburetting zone is preferably not less than 0.1 second or morethan 1.0 second. Within this range the risk of the temperature exceedingin places the lower limit at which cracking is possible, will be lowest.This lower limit is of course largely dependent on the residence time ofthe liquid carburant.

Carburetting is preferably carried out by passing liquid carburant intothe carburetting zone in a thin layer around a cooled rim along whichflows the hot gas from the gasification reactor. As the hot gas flowsalong the rim the carburant is absorbed by the gas and only becomescooled at the very last moment. Since the carburant passes around therim it does not make earlier contact with the flowing gas, so that thetemperature of the carburant can easily be kept low.

In order to achieve a gradual absorption of the carburant by the hotgas, which, according to the invention, substantially prevents theformation of coke or carbon accumulations, it is preferred to pass thecarburant in the carburetting zone in a thin layer for some distancealong a cooled wall alongwhich the said hot gas is flowing. In this casethe said cooled wall suitably ends in a sharp transition, the liquidcarburant being partly absorbed by the said hot gas on its way along thecooled wall and the rest being absorbed at the sharp transition. Sincecare is taken that during the contact with the hot gas the velocity ofthe carburant is not too high, no accumulation occurs. The velocity ofthe flow of hot gas in the carburetting zone is preferably between and1200 m/sec., the supply of carburant being such that the thickness ofthe layer of carburant film on the cooled wall is less than 1 mm. Theflow of the carburant along the said cooled wall is preferably in thedirection of flow of the hot gas.

In order to keep the temperature of the liquid carburant as low aspossible, it is preferably supplied to the carburetting zone in a thinlayer along a cooled wall along which the hot gas does not flow. Theliquid carburant is then suitably supplied along this cooled wall in adirection opposed to the direction of flow of the hot gas.

The invention is particularly suitable for a liquid carburant consistingof a petroleum fraction, such as gas oil, naphtha and kerosine. It isespecially these and similar carburants which tend to crack orpolymerize on the injection nozzle in the conventional process.

If in the way already described, the liquid carburant is supplied alonga cooled wall along which there is no flow of hot gas, and then passedfurther along a cooled wall along which there is a flow of hot gas up toa sharp transition where the liquid carburant is absorbed by the gas, itmay be advantageous to pass the liquid carburant around a free wallarranged in the carburetting zone which wall is internally cooled, thecarburant being introduced into the carburetting zone against the sidefacing the outside of the carburetting zone, then creeping round the endof the free wall and proceeding on the side of the free wall facing acenter line of the carburetting zone, before being absorbed in the gasflowing along the latter side. It is preferred to use a carburettingzone having a rotationally symmetrical or substantially rotationallysymmetrical construction, thus minimizing the risk of accumulations inthe carburetting zone.

As mentioned above, the carburetted gas is passed into a hydrogenator inorder to complete the desired reactions, i.e., to allow, inter alia, theevaporated carburant to further decompose and unsaturated compounds tobecome hydrated. The carburetted gas is very suitably passed into ahydrogenator where the gases are internally recirculated via an internaldivision of the hydrogenator.

An apparatus suitable for the production of gas having a calorific valueof more than 1000 kcal. lNm according to the process of the invention,as mentioned above, comprises a refractory gasification reactor for thepartial combustion of a fuel, a carburetting zone for carburetting thehot gas from the gasification reactor with a hydrocarbon carburant, ahydrogenation reactor to conduct the desired reactions in thecarburetted gas and optionally a waste heat boiler to cool the gas fromthe hydrogenator and produce steam. According to the invention thisapparatus is characterized by means for 6 passing liquid carburant in athin layer into the carburetting zone and at the same time cooling thecarburant.

The carburetting zone of the apparatus according to the invention ingeneral terms comprises a closed chamber, preferably cylindrical inshape, having (a) an inlet for introduction of the hot gas stream fromthe partial combustion zone whereby the flow of hot gas is directedalong the axis of the closed chamber parallel to the walls of the closedchamber; (b) an inlet for introduction of the hydrocarbon curburant bywhich the carburant enters the closed chamber at a directionperpendicular or opposed to the direction of the flow of hot gas andforms a thin film or layer on the surface of the closed chamber when .incontact with the hot gas; (c) a means for supplying external cooling,preferably by cooling devices in the chamber walls, to the surfaces ofthe closed chamber which are contacted by the thin layer of carburantwhich is also in contact with the hot gas flow; and (d) an outlet forwithdrawingthe carburetted hot gas mixture.

The carburetting zone of the above-mentioned apparatus, preferablycontains a rim with cooling devices wherein external cooling is suppliedto the surface of the rim and means for passing the carburant in liquidform around this rim, the rim being situated such that during operationthe hot gas from the gasification reactor flows along it.

The carburetting zone suitalbly contains a wall with cooling devices tosupply external cooling to the carburetting zone surface of the wall aswell as means for passing the liquid carburant along this wall, the wallbeing situated such that during operation the hot gas from thegasification reactor flows along it. This wall with cooling devicespreferably ends in a sharp transition. The liquid carburant is therebygradually absorbed by the hot gas. The carburetting zone preferablycontains a wall with cooling devices and means for introducing theliquid carburant into the carburetting zone along this wall, the wall[being situated such that during operation the hot gas does not flowalong it. With such a carburetting zone there is no risk ofaccumulations occurring and the carburant can be supplied gradually.

The carburetting zone is preferably provided with a free wall withinternal cooling devices which supply externally generated cooling tothe wall surface, one side directed outwardly perpendicular to the axisof the closed chamber and one side facing the axis of the closedchamber. Along the former side the liquid carburant is suitablyintroduced into the carburetting zone, while along the latter side theliquid carburant continues into the carburetting zone and makes contactwith the hot gas.

A functional apparatus is obtained when the carburetting zone has arotationally symmetrical or substantially rotationally symmetricalconstruction.

It is preferred to employ a carburetting zone provided with a cooled.venturi-shaped contraction. In the middle of this contractioninlongitudinal view the carburant supply is mounted, so that an outershell of the hot gas is pre-cooled in the first part of the venturi,before coming into contact with the cooled carburant film in the secondpart.

Referring to FIG. 1 the apparatus suitable for use in the process of theinvention comprises an empty refractory gasification reactor 1, providedwith a pipe 2 for the supply of fuel to the combustion chamber 3 of the7 reactor and with a supply pipe 4 for the oxygen.

The apparatus also comprises a reactor discharge 5 arranged as acarburetting zone, this also being empty and being partly provided withrefractory lining. The carburetting zone comprises a hydrocarbon supply6, through which liquid carburant can be supplied to the jacket 7.

By means of a flange 8 the discharge tube 5 is connected to ahydrogenator 9,10,11, consisting of two parallel columns 9 and 11, and abent intermediate pipe 10. This hydrogenator is empty and is entirelylined with refractory bricks. The columns 9 and 11 are connected to theintermediate pipe by means of flanges l2 and 13, respectively. The endof the upturned U- shaped hydrogenator is coupled to a waste heat boilerby means of a connection 14 and a flange 15.

This waste heat boiler consists of an empty-refractorybrick-lined-bottom vessel 16 and a steam boiler 17 mounted vertically onthe bottom vessel, which boiler is connected to the vessel 16 by meansof a flange 18. The steam boiler is equipped with a water supply 19 nearits base and a discharge 20 for high-pressure steam at its top. Throughthe stem boiler 17 runs a helically wound gas pipe 21, whichcommunicates with the bottom vessel 16 via the straight bottom end 22and which passes through the boiler wall at the top via the gasdischarge 23.

In carrying out the process according to the invention the apparatusshown in FIG. 1 operates as follows.

The fuel supplied via 2 together with less than the theoretical amountof oxygen is incompletely burned in reactor 1. An amount of steam mayoptionally be supplied via the bumer or by other means. A crude gasstream leaves the reactor via 5 at a temperature of approximatelyl200l400C. This gas usually contains some soot and mainly compriseshydrogen and carbon monoxide. However, inter alia, water vapor, carbondioxide, hydrogen sulfide are also usually present.

This hot crude gas is then carburetted in the discharge tube 5. The gasshould usually first be cooled below 1100C. It is also advantageous foran excess amount of water vapor to be present in the gas. To this end anamount of water is suitably injected into the tube 5 via 24 or into thebottom of the reactor via 25. A liquid carburant in the form of ahydrocarbon fraction is then injected into the gas in one or more steps.If carburetting is carried out in several steps it is possible to injectadditional water between two steps in order to cool the gas and toincreaese the amount of water vapor present.

After the gas has been carburetted the desired reactions take place inthe hydrogenator 9, 10, 11. Here any drops of liquid carburant stillpresent evaporate, unsaturated hydrocarbons are hydrogenated, a certainmethanization takes place, and hydrocarbons react with steam whileforming hydrogenand carbon monoxide.

The crude carburetted gas which now contains a not inconsiderablepercentage of methane, is passed into the bottom vessel of the wasteheat boiler at a temperature between about 800C and 1100C, eventuallyleaving this waste heat boiler at a temperature of usually less than400C. The waste heat boiler produced steam under a considerablepressure.

It will be understood that within the scope of the invention manyalterations can be made of the apparatus shown. For example, thehydrogenator may be of an entirely different shape, and, for example, bearranged in a horizontal plane instead of vertically. The waste heatboiler may also be different and, for example, have a number of helicalgas pipes instead of one, have a differently shaped bottom vessel, oremploy another coolant. It may also be of a completely different type.

An embodiment of the carburetting apparatus according to the inventionis shown in detail in FIG. 2. FIG. 2 represents a horizontal partialcross-section of the carburetting apparatus taken along line 22 inFIG. 1. For clarity and convenience the carburetting zone jacket 7 inFIG. 1 is not shown in FIG. 2. However, it will be understood that thisjacket surrounds the apparatus shown in partial cross-section includingthe discharge tube 5 which is shown. A cylindrical inner wall 26 of thedischarge tube 5 is provided with a refractory lining 33 of thecarburetting zone in order to allow flow of the hot gas to becarburetted in flre direction indicated by the arrow. In the refractorylining 33 there is a ring groove 27 for the supply of liquid carburant.For the further flow of the carburant and to insure the desired supplyof carburant in the form of a thin film a cooled wall 28 with acylindrically inverted inner part 29 projecting freely in the route ofthe flowing gas is arranged in the groove 27. Further, a Z-shapedprofiled and cooled ring 30 is arranged under the ring (28,29) so as toform a Z-shaped slit 31. The carburant is introduced into thecarburetting zone via this slit. The side of the cooled wall (28,29)facing the ring 30 and the slit 31, faces the outside of thecarburetting zone and the hot gas does not flow along it. The side 32 ofthe cooled wall 29 freely mounted in the carburetting zone on the otherhand is facing the center line of the carburetting zone; and the hotgases flow along it. A suitable coolant is circulated through thepassageways 50 and 51 to cool the walls 28,29 and 30 by conduit meanscoupled to the openings between the walls (not shown in FIG. 2).

When the apparatus is in operation the liquid carburant is passed intothe carburetting zone in a thin layer via the cooled slit 31, that is tosay, via the rim 34 to the side 32 along which the hot gas is flowing.At 35 there is a sharp transition where the remaining liquid carburantcan be absorbed by the hot gas. Part of the liquid carburant is alreadyabsorbed by the hot gas between the rims 34 and 35.

The carburetting zone may be constructed differently and possess, forexample, differently shaped walls for the introduction of liquidcarburant.

FIG. 3 is a diagrammatic illustration of such an alternativecarburetting zone.

the connecting tube 36, which connects the gasification reactor (notshown) with the hydrogenator 37, contains a carburetting zone. This tube36 has a cooled rotationally symmetrical restriction 38, 39, which issituated on either side of a ring slit 40 for the supply of liquidcarburant. The hot gas to be carburetted flows into the carburettingzone via the jacket 7 and through the tube 36in the direction indicatedby the arrow, and the carburant is supplied to the ring slit 40 in thedirection likewise indicated. The liquid carburant then enters thecarburetting zone in a thin layer along the inner side 41 of the cooledwall 38along which the hot gas is also flowing. The cooling of the wallsof the striction 38 and 39 is diagrammatically illustrated by the watershells 42 and 43. w

A particular advantage of this embodiment of the carburetting zone isthat the part of the hot gas that comes into contact with the carburantfilm on the wall 38 is cooled in advance on wall 39.

9 After having been carburetted the gas enters the hydrogenator 37 viaconnecting tube 36, and is hydrogenated. The gas subsequently passesfrom the hydrogenator to a waste heat boiler (not shown) to be cooled.

We claim as our invention:

l. A process for the production of town gas which comprises a. partiallycombusting a carbonaceous fuel selected from the class consisting ofheavy fuel oil, petroleum distillates or residues, liquid fuelcontaining process soot and slurries of coal grit in water in a partialcombustion zone to produce a hot gaseous product containing hydrogen andcarbon monoxide;

b. carburetting the hot gas product of the partial combustion zonemaintained at a temperature of between 700 and 1 100C with a volatileliquid hydrocarbon carburant in a carburetting zone thereby effectingvolatilization of the carburant into the hot gas and the accompanyingthermal cracking of the carburant into methane and lighter unsaturatedhydrocarbons, said liquid carburant having a residence time in thecarburetting zone 10 between about 0.1 and 10 seconds and beingintroduced into the carburetting zone in the form of a thin layermaintained at a. temperature below that at which thermal cracking occursduring the time the carburant is not absorbed by the hot gas;

c. passing the carburetted product of the carburetting zone into ahydrogenation. zone maintained at ele vated temperatures wherein anyremaining volatilized hydrocarbon carburant is further decomposed bythermal cracking and the unsaturated hydrocarbon compounds arehydrogenated and;

d. cooling the hot gaseous product of the hydrogena tion zone.

2. The process of claim 1 wherein the liquid hydrocarbon carburant ismaintained as a thin layer below the cracking temperature of thecarburant while in contact with the hot gas by means of external coolingsupplied to' all of the carburetting zone surfaces with which the thinlayer of carburant comes into contact with during the time that saidcarburant is also in contact with the hot gas.

1. A PROCESS FOR THE PRODUCTION OF TOWN GAS WHICH COMPRISES A. PARTIALLYCOMBUSTING A CARBONACEOUS FUEL SELECTED FROM THE CLASS CONSISTING OFHEAVY FUEL OIL, PETROLEUM DISTILLATES OR RESIDUES, LIQUIDS FUELCONTAINING PROCESS SOOT AND SLURRISES OF COAL GRIT IN WATER IN A PARTIALCOMBUSTION ZONE TO PRODUCE A HOT GASEOUS PRODUCT CONTAINING HYDROGEN ANDCARBON MONOXIDE, B. CARBURETING THE HOT GAS PRODUCT OF THE PARTIALCOMBUSTION ZONE MAINTAINED AT A TEMPERATURE OF BETWEEN 700* AND 1100*CWITH A VOLATILE LIQUID HYDROCARBON CARBUTANT IN A CARBURETTING ZONETHEREBY EFFECTING VOLATILIZATION OF THE CARBUTANT INTO THE HOT GAS ANDTHE ACCOMPANYING THERMAL CRACKING OF THE CARRBUTANT INTO METHANE ANDLIGHTER UNSATURATED HYDROCARBONS, SAID LIQUID CARBURANT HAVING ARESIDENCE TIME IN THE CARBUTTING ZONE BETWEEN ABOUT 0.1 AND 10 SECONDSAND BEING INTRODUCEED ONTO THE CARBURETTING ZONE IN THE FORM OF A THINLAYER MAINTAINED AT A TEMPERATURE BELOW THAT AT WHICH THERMAL CRACKINGOCCURS DURIN THE TIME THE CARBURANT IS NOT ABSORBED BY THE HOT GAS, 2.The process of claim 1 wherein the liquid hydrocarbon carburant ismaintained as a thin layer below the cracking temperature of thecarburant while in contact with the hot gas by means of external coolingsupplied to all of the carburetting zone surfaces with which the thinlayer of carburant comes into contact with during the time that saidcarburant is also in contact with the hot gas.